Electronic devices include traditional computing devices such as desktop computers, notebook computers, smartphones, wearable devices like a smartwatch, internet servers, and so forth. However, electronic devices also include other types of computing devices such as personal voice assistants, thermostats, automotive electronics, robotics, devices embedded in other machines like refrigerators and industrial tools, Internet-of-Things (IoT) devices, and the like. These various electronic devices provide information, entertainment, social interaction, security, safety, productivity, transportation, and other services to human users. Thus, electronic devices play crucial roles in many aspects of modern society.
Many of the services provided by electronic devices in today's interconnected world depend at least partly on electronic communications. Electronic communications can include those exchanged between or among distributed electronic devices using wireless or wired signals that are transmitted over one or more networks, such as the Internet or a cellular network. Electronic communications can also include those exchanged between or among different printed circuit boards, modules, chips, or even cores of a given integrated circuit that are within a single electronic device. Regardless, electronic communications are usually accomplished by generating or propagating signals. Such electronic communications are typically performed using at least one signal that is designed to have a specified characteristic, such as a particular frequency. Generally, communication signals are more likely to be correctly transmitted and received, as well as properly interpreted, if the specified signal characteristic is accurately created and reliably maintained.
With regard to a frequency signal characteristic, a phase locked loop (PLL) can be used to create, or synthesize, a desired frequency. In fact, a PLL is a core part of many frequency synthesizers. A frequency synthesizer is a component that is employed by electronic devices to synthesize signals having different frequencies. In operation, a PLL receives a reference signal and applies the reference signal to a feedback loop. Using the feedback loop, the circuitry of the PLL generates an output signal that oscillates at a desired frequency in a stable and accurate manner based on the reference signal. Typically, the PLL derives the frequency of the oscillating output signal from the reference signal, such as by generating an output frequency that is some multiple of a frequency of the reference signal.
A PLL-based frequency synthesizer thus outputs an oscillating signal having some desired frequency. The electronic device then uses the synthesized frequency of the oscillating output signal in one or more stages of a communication scenario. Example stages for communicating an electromagnetic signal include generating, transmitting, receiving, or interpreting a communication signal. In an example signal-generation stage, a frequency generated by a PLL can be used to modulate a communication signal. Here, the modulation entails encoding or adding information to the communication signal. In an example signal-transmission stage, the frequency generated by a PLL can be employed to upconvert a frequency of a communication signal using a mixer. With an up-conversion operation, the mixer increases the frequency of the communication signal, such as to enable the communication signal to be transmitted wirelessly as a radio frequency (RF) signal between a smartphone and a cellular base station.
A PLL can also be used with the stages of a reception side of a typical communication scenario. For instance, a PLL can be used to down-convert a frequency of a received communication signal or to demodulate the received communication signal to recover the encoded information. Additionally, a PLL can be used to produce a clock signal that controls a rate of operation of circuitry on an integrated circuit, such as a system-on-chip (SoC) that processes a communication signal or a graphics chip that processes video data that is being displayed to an end user.
Thus, PLLs are employed in multiple stages of a communication scenario to support electronic communication with electronic devices. Other types of locked loops, such as frequency locked loops (FLLs) and delay locked loops (DLLs), are also instrumental in the proper functioning of electronic devices. Consequently, electrical engineers and other designers of electronic devices strive to improve the functionality and usability of locked loops to facilitate electronic communication with electronic devices.